Preparation of haloalkyl aromatic hydrocarbons

ABSTRACT

Process for alkylating an aromatic hydrocarbon by reacting a haloalkane with either benzene or an alkyl benzene and conducting the reaction in the presence of an alkylaluminum halide catalyst without deliberately adding heat to elevate the temperature of the reaction.

United States Patent Nelson 1 *Apr. 1, 1975 PREPARATION OF HALOALKYL 2.355.850 8/1944 Dl'ClSbtlCh 260/651 HA AROMATIC HYDROCARBONS 2.388.428 11/1945 Mavity 260/448 A 2.631.172 3/1953 schnierlin 260/651 HA 1 1 Inventor: Gunner R Nelson, Baton ge. a. 2.794.822 6/1957 Schweitzc? 260/668 0 6 I 3.031.514 4/1962 Kosmin 260/671 C [73] Ass1gnee. Ethyl Corporation. Rlchmond. Va. 1094568 6/1963 Hay ct H 260/671 C I Notice: The portion of the tern of Winklcr P patent Subsequent to J 22 1991 3.312.748 4/1967 Johnson 260/671 R has been disclaimed. Pl d A 11 1973 OTHER PUBLlCATlONS 1e pr.

Schmerling et a1.. JACS. 79. pp. 2636-2642. May 20. [21] Appl. No. 349.927 I957.

Related US. Application Data [60] Division of Scr. No. 123.037. March 10. 1971. Pat. p m E C D i torney. Agent. or Firm-Donald L. Johnson; John F. continuation-in-part of Scr. No. 568.779. July 29. Sleberth; Edgar E. Splelman' Jr' 1966. abandoned.

1521 11s. c1... 260/651 HA, 260/651 R, 260/668 c. 1571 ABSTRACT 7 I t Cl I ag 2 Process for alkylating an aromatic hydrocarbon by re- {581 H 448 R acting a haloalkane with either benzene or an alkyl le 0 earc 6 C 6 668 I benzene and conducting the reaction in the presence of an alkylaluminum halide catalyst without deliber- References cued ately adding heat to elevate the temperature of the reaction. UNITED STATES PATENTS 2.308.419 1/1943 Hcitz ct a1 260/651 HA 6 Claims. N0 Drawings PREPARATION OF HALOALKYL AROMATIC HYDROCARBONS CROSS-REFERENCE TO RELATED APPLICATION This is a division of application Ser. No. D1037 filed Mar. 10. 1971. now L'.S. Pat. No. 3.787.5l2. which is a continuation-in-part of application Ser. No. 8 13.340. filed Apr. 3. 196), which is a continuation-in-part of application Ser. No. 568.779. filed July 29. 1966, the latter two of which are now abandoned.

BACKGROUND OF THE INVENTION This invention relates to the preparation of aromatic hydrocarbons through use of aluminum alkyl halides as Friedel-Crafts catalysts. By way of example. this invention concerns a method for forming an w-haloalkylbenzene or a p-alkylw-haloalkylbenzene by reacting an mw-dihaloalkanc with. respectively. benzene or an alkylbenzene in the presence of a diluent and an aluminum alkyl halide catalyst. Further. this invention concerns a method for forming an am-diphenylalkane or an a.w(p.p'-alkyldiphenyl )alkane by reacting an a,w-dihalolakane with, respectively, benzene or an alkylbenzene in the presence of an aluminum alkyl halide catalyst. In addition. this invention provides a method for forming a monoalkylbenzene or polyalkylbenzene by reacting a monohaloalkane with. respectively, benzene or an alkyl benzene in the presence of a diluent and an aluminum alkyl halide catalyst; absence of a diluent leads to the formation of other polyalkylbenzenes. Other alkylation reactions contemplated by the present invention will become apparent from the following description.

The compounds developed by the process of the present invention find use both as scavengers for alkyl lead antiknock agents (see U.S. Pat. Nos. 1,668.02! and 2.398,28l) and as pesticides when properly applied as a spray or dusting powder.

The prior art has been beset with two major problems in reactions of the types involved in the present invention, namely. yield of the desired products has been quite low and reaction temperatures have been necessarily quite high, thus increasing the number of undesirable impurities in the product. Prior art reactions have been conducted using conventional Friedel-Crafts catalysts such as. for example. aluminum chloride. Literature references involving such standard Friedel-Crafts catalysts report temperature requirements of 70C. and higher.

A purpose of the present invention is to overcome the above-noted disadvantages of the prior art. More specifically, a purpose of the present invention is to produce high yields of the desired aromatic hydrocarbons while conducting the requisite chemical reactions at economically low temperatures. Further advantages and purposes of the present invention will become apparent in the following description.

SUMMARY OF THE INVENTION The present invention provides a process for alkylating an aromatic hydrocarbon by reacting a haloalkanc with a compound selected from the group consisting of benzene and alkyl benzenes comprising conducting the reaction in the presence of an alkyl-aluminum halide catalyst and avoiding the deliberate addition of heat to elevate the reaction temperature.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is drawn to several species of alkylation reactions. four of which utilize an tun-dihaloalkane as one reactant and either benzene or an alkylbenzene as the other reactant. Two species of the reactions which produce. respectively. an w-haloalkylbenzene when benzene is a reactant and a p-alkyl-whaloalkylbenzene when an alkylbenzene is reactant. utilize an organic diluent. Another two species of the reactions which produce. respectively. an lY.(U-LIIPITCI])- lalkane when benzene is a reactant and mw-t p.p-alkyldiphenyl )alkane when an alkylbenzene is a reactant. do not utilize a diluent. Still another two species of the reactions. which employ a monohaloalkane as one reactant and either benzene or an alkylbenzene as the other reactant to produce. respectively. a monoalkylbenzene or polyalkylbenzene. also employ a diluent: absence of the diluent in either of these two reactions leads to the formation of other polyalkylbenzenes. The remaining species ofthe reactions are similar to the first four reactions with the exception of employing mw-dihaloalkanes having different halogens or polyhaloalkanes having more than three halogens which are the same or different. All of the reactions employ as a catalyst one or a combination of dialkylaluminum halide and/or alkylaluminum dihalide.

Preferred reactions are first, the reaction of l.2- dichloroethane with benzene in the presence of an organic diluent and methylaluminum sesquichloride to produce B-chloroethylbenzene; second. the reaction of l,Z-dichloroethane with toluene in the presence of an organic diluent and methylaluminum sesquichloride to produce p-methyl-Bchloroethylbenzene; third. the reaction of l,2-dichloroethane with benzene in the presence of methylalumimim sesquichloride to produce l.Z-diphenylethane; fourth, the reaction of dichloroethane with toluene in the presence of methylaluminum sesquichloride to produce l,2-(p,p"- methyldiphenyl)ethane; fifth, the reaction of methyl chloride with benzene in the presence of methylaluminum sesquichloride and. a diluent to produce toluene: and sixth. the reaction of methyl chloride with toluene in the presence of methylaluminum sesquichloride and a diluent to produce l,4-dimethylbenzene. The order of stating the reactions above does not indicate an order of preference.

The improvement of the present invention flows primarily from the use in alkylation reactions of alkylaluminum halide catalysts, a preferred catalyst being methylaluminum scsquihalide, which is a mixture of dimethylaluminum halide and methylaluminum dihalide. The organoaluminum catalysts employed in this invention include compounds having the formula R,,AIX wherein R represents a hydrocarbon selected from the group consisting of alkyl and aryl radicals. X represents a halogen selected from the group consisting of chlorine, bromine and iodine, and n represents an integer not greater than 3. Thus, the invention contemplates the use of all organoaluminum halides of the type RAIX and R- ,AIX and mixtures of the same (cg. sesquihalides). In compounds of the R- AIX type, the R groups may be the same or different, c.g. (CH;,)(C- ,H )AIX. These catalysts cause the above reactions to proceed at a relatively fast rate at comparatively low temperatures which need not exceed room tentpcratures, and thus, no heating is required in the present invention as is generally required as taught by the prior art. Conventional Friedel-Crafts catalysts, such as aluminum chloride, not only require supplying heat to the reaction but tend to remain in suspension in the reactants thus leading to slow reactions. On the other hand. alkylaluminum halide catalysts are readily soluble in the reactants and are conducive to fast reactions, good conversions and high yields. The molar ratio of reactants to catalyst may range from about 0.05 to 0.1 to about 5 to 0.1; preferably it will range from about ().l to 1.0 to about 2 to (H In continuous opera tion processes, the catalysts of the present invention may be easily recovered and recycled for continuing use.

Numerous diluents are suitable for those reactions of the present invention which require a diluent. Typical organic diluents are ligroin, nitrobenzene, carbon disulfide. hexane. and isooctane. In general, all paraffinic hydrocarbons which are liquid at reaction temperature are suitable. All useful diluents must be liquid at reaction temperatures and inert to the reactants of the present invention. Generally, 50 percent to 80 percent by volume of the reactant solution is diluent.

A broad range of monohaloalkanes are useful in some of the reactions of the invention. Exemplary are compounds having up to about carbon atoms, c.g., methyl chloride, methyl bromide, ethyl chloride, propyl bromide, butyl chloride, pentyl bromide. decyl bromide, 6-111Cll1Yl-lCl1lOl'O(lCCZll]C, and the like. Preferred haloalkanes have from 2 up to about 4 carbon atoms.

A comparatively wide variety of a,w-dihaloalkane re actants may be used in some of the present invention. Typical a,w-dihaloalkanes have from 2 up to about 20 carbon atoms and include such compounds as 1,2- dichloroethane, l.2-dibromoethane, l,2-diiodoethane, 1,2-dichloropropane, l,4-dichlorobutane, and l,Z-dichIoro-Z-methylpropane, l,5-dichloropentane, l ,8-dibromooctane, l ,1 (l-dichlorodecane, l,lO-dibromo-b-ethyldecane, and the like. Preferred a.w-dihaloalkz1t1es have from about 2 up to about 4 carbon atoms, with the most preferred a,w-dihaloalkane being l,2-dichloroethane.

Polyhaloalkanes other than a,w-dihaloalkanes having two or more halogens which may be the same or different are also useful in the practice ofthe invention. Such haloalkancs preferably have from I up to about 20 carbons and preferably up to about 4 carbon atoms. Exemplary are chloroform, bromoform, methylene chloride,

methyl chloroform, I,l,Z-trichloroethane, l,l,2,2- tetraiodoethane, l, l l ,Z-tetrabromoethane, 1,1,3- trichloropropane, l,l ,4-triiodobutanc, l ,l l0- trichlorodecane, chlorobromoethane, l-chloro-3- bromo-(i-iodohexane, and the like.

The present invention also lends itself to a relatively wide variety of alkylbenzene reactants having from 7 up to about carbon atoms and preferably up to about 1() carbon atoms; such reactants may include one or several alkyl radicals which are the same or different. Typical alkylbenzenes include toluene, ethylbenzene, p-ethylpropylbenzene, propylbenzene, butylbenzenc, isopropylbenzene, isobutylbenzene and decylbenzene, with a preferred alkylbenzene being toluene.

Having thus set forth the present invention, the following examples are presented as being further descriptive of the present invention, though not as limiting thereof:

EXAMPLE 1 One mol of benzene was reacted with 0.2 mol of l,2- dichloroethane in the presence of 0.] mol of methylaluminum sesquichloride and a hexane diluent at 25C. to produce predominantly B-chloroethylbenzene.

EXAMPLE ll One mole of benzene was reacted with 0.5 mol of 1,2-dichloroethane in the presence of 0.2 mol of methylaluminum sesquichloride at 25C. to produce a percent yield of l,Z-diphenylcthane.

EXAMPLE lll One mol of toluene was reacted with 0.2 mol of 1,2- dichloroethane in the presence of 0.1 mol of methylaluminum sesquichloridc and a hexane diluent at 25C. to produce predominantly p-methyl-B-chloroethylbenzene.

EXAMPLE lV One mol of toluene was reacted with 0.5 mol of 1,2- dichloroethane in the presence of 0.2 mol of methylaluminum sesquichloride at 25C. to produce predominantly l,2-(p,p-methyldiphenyl)ethane.

The following examples may be carried out under the listed conditions to yield predominantly the product noted.

I claim:

I. A process for producing w-haloalkyl benzene or p-alkyl-m-haloalkyl benzene by reacting a-w-dihaloalkane with, respectively, benzene or alkyl benzene in the presence of a diluent and alkylaluminum halide catalyst whereby the addition of heat to the reaction is not necessary to effect a high reaction rate.

2. The process of claim 1 wherein the diluent is a paraffinic hydrocarbon which is liquid at reaction temperatures.

3. The process of claim 1 wherein the a-w-dihaloalkane is 1,2-dichloroethane.

4. The process of claim 1 wherein the alkylaluminum halide catalyst is methylaluminum sesquichloride.

5. The process of claim I wherein the alkyl benzene is toluene.

6. The process of claim 1 wherein the diluent is a paraffinic hydrocarbon which is liquid at reaction temperatures, the a-w-dihaloalkane is 1,2-dichlor0ethane, the alkylaluminum halide catalyst is methylaluminum sesquichloridc and the alkyl benzene is toluene. 

1. A PROCESS FOR PRODUCING W-HALOALKYL BENZENE OR P-ALKYLW-HALOALKYL BENZENE BY REACTING A-W-DIHALOALKANE WITH, RESPECTIVELY, BENZENE OR ALKGL BENZENE IN THE PRESENCE OF A DILUENT AND ALKYLALUMINUM HALIDE CATALYST WHEREBY THE ADDITION OF HEAT TO THE REACTION IS NOT NECESSARY TO EFFECT A HIGH REACTION RATE.
 2. The process of claim 1 wherein the diluent is a paraffinic hydrocarbon which is liquid at reaction temperatures.
 3. The process of claim 1 wherein the Alpha - omega -dihaloalkane is 1,2-dichloroethane.
 4. The process of claim 1 wherein the alkylaluminum halide catalyst is methylaluminum sesquichloride.
 5. The process of claim 1 wherein the alkyl benzene is toluene.
 6. The process of claim 1 wherein the diluent is a paraffinic hydrocarbon which is liquid at reaction temperatures, the Alpha - omega -dihaloalkane is 1,2-dichloroethane, the alkylaluminum halide catalyst is methylaluminum sesquichloride and the alkyl benzene is toluene. 